Methods of finishing cellulosic fabrics



Patented June 12, 1945 UNITED STATE s PATENT. OFFICE METHODS OF FINISHING CELLULOSIC FABRICS Harold I. Huey, Saylesville, and William W. Russell, East Providence, R. 1., assignors to Sayles Finishing Plants, Inc., Saylesviile, R. I., a corporation of Rhode Island No Drawing. Application November 4, 1942, Serial No. 464,518

Claims. (Cl. 8-115.6)

printed or pigmented, if desired.

We have discovered a method for finishing cotton cloth which imparts to the cloth properties of fullness, resiliency and warmth of hand resembling those of a wool fabric, and of fineness like that of linens, properties which such cloth naturally does not pos ess and which materially enhance its attractiveness, usefulness and salability. In some respects the new finish imparts to cotton the best aspects of a spun rayon fabric but our finished fabric is much more serviceable than the rayon fabric. The new properties thus produced are of a lasting character and remain inthe cloth despite repeated launderings or dry cleanings.

We have found that these new and highly de-' sirable properties are imparted to the cloth 'by a processof impregnating the cloth with relatively dilute, basic solutions of certain cellulose derivatives, fixing the cellulose or the cellulose derivative in the cloth and shrinking the clothv with caustic, provided that, after impregnation with the cellulosic solution and priorto fixation, the impregnated cloth is subjected to a controlled heating which removes some but not all of the water or other volatile medium of the solution, and fixation then takes place while the fabric is still wet or moist;

In practicing the method of the invention, the

' cloth, prior to impregnation with'the cellulosic solution, is rendered reasonably absorbent, through removal of fats, waxes, gums and like repellent substances, by any or all of the steps of scouring, boiling, kiering and bleaching.

' The cloth, preferably after drying, .is then impregnated with the cellulosic solution. which is preferably aqueous and contains a strong base and one or more alkali-soluble cellulose derivatives, such as cellulose xanthate, hydroxy ethers on other compounds of cellulose and the like, or

cellulose so modified as to be soluble in, or at least strongly swollen by, strong alkali. The base Other 010- duces a finished fabric which can be readily dyed,

is preferably sodium hydroxide, but such other strong bases as potassium or lithium hydroxide or certain quaternary bases may be used. Con-.

centrations of from 4 to 9% by weight of base and 1 to 3% by weight of cellulose for the impregnating solution have been found suitable. Aqueous'solutions of about 6% by weight of sodium hydroxide and 1.5% by weight of cellulose in the form of xanthate, or about 7% by weight of sodium hydroxide and about 1,5% cellulose hydroxy ether are preferred.

After this impregnation, the cloth may be squeezed, leaving, however, a substantial quantity of the impregnating solution in the goods,

about 100% gain in weight being a suitable amount in the case of typical fabrics.

The impregnated cloth is now heated under carefully controlled conditions to an extent suflicient to drive off some but not all of the water or other volatile medium of the solution. A preierred practice of this step, consists of heating the cloth just sufficiently to evaporate approximately 50% of the moisture-from thev cloth, as may be done conveniently by running the cloth rapidly over hot drums. Inno event should less than 20% or more than of the moisture be removed from the cloth.

After heating, the cloth, while still warm and moist, is treated to fix the cellulose or cellulose derivative in the fabric, either with an acid, such as sulphuric, hydrochloric, nitric orperchloric or other mineralacids, or acid salts, or with sufiiciently strong alkali such as caustic soda, caustic potash, etc. Where cellulose xanthate is used in theimpregnatin'g solution, fixation will ordinarily be by the acid or souring treatment which may be at normal or elevated temperature and which may include 'a water wash to remove the acid after fixation is completed.

Where the cellulosic impregnating solution is 7 of the type which is readily precipitated not only by acids, but also by strong alkali, the acid-fixation step may, if desired, be omitted and fixation will automatically take place during the next step in the process so'that a separate fixation treatment is unnecessary. This next step consists in swelling and shrinking the cloth by treating the cloth'with strong caustics such as those previously mentioned, preferably an aqueous solution of sodiumiiydroxide, and relaxing the cloth without tension for a sufilcient, interval to allow substantial swelling and shrinking of the cloth to take place, as by resting the cloth loosely on a conveyor. The concentration of the sodium hydroxide solution should be of, or somewhat below,

width on a tenter, etc., in the usual manner. In

some cases, the fabric may be run one or more times through a breaker.

The finished fabric possesses to a marked extent, readily apparent to those accustomed to the handling of fabrics, a fullness, resiliency and warmth of hand characteristic of wool, a fineness characteristic of linen and some of the most desirable characteristics of spun rayon. qualities are enduring and will last for substantially the full life of the fabric under normal conditions of use and cleaning.

Controlled reduction by heat of the moisture content of the fabric, within the limits previously mentioned, after impregnation with the cellulosic solution and prior to fixation we have found to be critical to the attainment of these new properties. Thus, if the impregnated fabric is dried in this stage, the process being otherwise unchanged, there is produced a stiff, wiry finish having none of'these new qualities. On the other hand, if the cellulose or cellulose derivative is fixed in the fabric without this critical reduction of moisture content by heating, the process being otherwise unaltered, there is little detectable change produced in the natural properties of the cloth.

While we are uncertain as to the reason why it is critical in the process to remove moisture in the specified range by heating prior to fixation, we believe that it is because this step creates a condition in which just the proper amount of penetration of the cellulose or cellulose derivative particles into the yarns and fibres of the fabric takes place, so that the fibres are to some extent reenforced, but are not cemented together and stiffened, when the cellulose or cellulose derivative is fixed or precipitated.

We have also found some shrinkage of the fabric with strong caustic after or during the fixation treatment to be essential to the process, as

the new qualities described do not appear in any noticeable degreeif this step is omitted, or is substituted by a mercerizing treatment, in which the cloth is held under tension. The amount of shrinkage obtained in this mannermay vary considerably but should usually be substantial. For example, operating with cotton cloth counting 76 x72 and weighing 9 yards per pound and employing the preferred shrinking'caustic solution, (an aqueous solution of sodium hydroxide, 48 Twaddell), the shrinkage of the finished cloth may be about 6 to 12% loss in original length and about 12% loss of the initial width.

The fabric may be dyed, printed or pigmented prior to impregnation with the cellulosic solution and, with some care in the choice of dyestufis, little or no color change will be produced in the process. One advantage of the process, however, lies in the fact that any of these operations may be performed satisfactorily on the finished fabric. The cellulosic solution may, if desired, include fillers, softeners, pigments, etc. While concen- These tration of the celluloisic solution may vary to some extent with the nature of the cloth being treated and with the cellulose derivative and caustic used, it should ordinarily be kept within the limits previously mentioned, as greater concentrations are apt to result in excessive stiffening and lesser oncentrations to produce no desirable effects.

While the invention is particularly adapted to the finishing of cotton fabrics, it also has advantages for the finishing of other fabrics such as those made up wholly, or partly, of fibres of cellulose derivatives, of flax and of certain artificial polymers.

The term cellulose derivative as used in this specification and in the appended claims is to be understood to include cellulose xanthate, hydroxy ethers or other compounds or modifications of cellulose and the like.

Having described a preferred practice of the method of the invention, what we desire to claim and secure by Letters Patent is:

1. A process for imparting a durable, refined,

resilient compacted finish to cotton cloth which comprises impregnating the cloth with an alkali solution of cellulose derivative, said solution containing 1 to 3% by weight of cellulose, heating the impregnated cloth to an extent sufilcient to remove not les than 20% nor more than of the 'moisture from the cloth and, with the cloth in this condition of moisture, precipitating thereon and therein at least the cellulose from the impregnant solution, and shrinking the cloth .by treating it in a relaxed condition to the action of a strong caustic.

2. A process for imparting a durable, refined, resilient compacted finish to cotton cloth which comprises impregnating the cloth with an aqueous alkali solution of cellulose derivative, said solution containing approximately 1.5% by weight of cellulose, heating the impregnated cloth to an extent sufficient to remove not less than 20% nor more than 80% of the moisture from the cloth and, with the cloth in this condition of moisture, precipitatin thereon and therein at least the cellulose from the impregnant solution, and shrinking the cloth by treating it in a relaxed condition to the action of a Strong, caustic.

3. A process for imparting a durable, refined, resilient compacted finish to cotton cloth which comprises impregnating the cloth with an aqueous alkali solution of cellulose derivative, said solution containing approximately 1.5% by weight of cellulose, heatin the cloth impregnated with about its weight of the solution to an extent sufficien't to remove at least about half, but not more than 80%, of the moisture from the cloth and, with the cloth in this condition of moisture, precipitating thereon and therein at least the cellulose from the impregnant solution, and shrinking the cloth by treating it in a relaxed condition to the action of a strong caustic.

4-. A process for imparting a durable, refined, resilient, compacted finish to cotton cloth which comprises impregnating the cloth with an aqueous alkali solution of cellulose xanthate, said solution containing about 1.5% by weight of cellulose and 4 to 9% by weight of a strong base, heating the impregnated cloth to an extent sufficient to remove at least about half, but not more than 80% of the moisture from the cloth, and, with the cloth in this condition of moisture, precipitating cellulose from the solution in the cloth by treating the cloth with an acid solution, and

shrinking the cloth by treating it in a relaxed condition to the action 0! a strong caustic.

5. A process for imparting a durable. refined, resilient, compacted finish to cotton cloth which comprises impregnating the cloth with an aqueous alkali solution of cellulose hydroxy ether, said solution containing 1 to 3% by weight of cellulose, heating the impregnated cloth to an extent sumcient to remove not less than 20% .nor

more than 80% of themoisture from the cloth and, with the cloth in this condition of moisture, precipitating therein and thereon cellulose hydroxy ether from the solution by treating the cloth with a strong base, and shrinking the cloth by treating it in a relaxed condition to the action of a strong caustic.

HAROLD I. HU'EY.

WILLIAM W. RUSSELL. 

